I can almost guarantee that I know what was going through their heads. They thought this was a test from God to see if they would REALLY trust him, even after he let one of their children die. This was to prove God's sovereignty over everything in their life, including those things most precious to them.
And I have no doubt that the peer pressure to remain "faithful and strong" was huge.
I have heard it before in real life and I know their tactics to subdue common sense.
However, as much as I understand craziness like this, I have no patience or compassion for it. They ought to have been in jail after the first one. I only hope their remaining children will be able to see reality and not carry on this horrible belief system.